getch() implementation in Unix

[ahamed101]

Hi Everyone,

I know conio.h is not available in Unix. I want to use getch(). Using curses.h needs causes the screen to clear which I don't want.

I found a code snippet (source : internet) using termios, it works, the thing is I need to press enter/or any other key thrice...

#include <stdio.h>
#include <termios.h>
#include <unistd.h>

int mygetch ( void ) 
{
  int ch;
  struct termios oldt, newt;
  
  tcgetattr ( STDIN_FILENO, &oldt );
  newt = oldt;
  newt.c_lflag &= ~( ICANON | ECHO );
  tcsetattr ( STDIN_FILENO, TCSANOW, &newt );
  ch = getchar();
  tcsetattr ( STDIN_FILENO, TCSANOW, &oldt );
  
  return ch;
}

Any help on this would be of great help...

[Salem]

Can you show a small program where you call mygetch, and you have to press return twice

[Sci@phy]

Hi Everyone,

I know conio.h is not available in Unix. I want to use getch(). Using curses.h needs causes the screen to clear which I don't want.

I found a code snippet (source : internet) using termios, it works, the thing is I need to press enter/or any other key thrice...

#include <stdio.h>
#include <termios.h>
#include <unistd.h>

int mygetch ( void ) 
{
  int ch;
  struct termios oldt, newt;
  
  tcgetattr ( STDIN_FILENO, &oldt );
  newt = oldt;
  newt.c_lflag &= ~( ICANON | ECHO );
  tcsetattr ( STDIN_FILENO, TCSANOW, &newt );
  ch = getchar();
  tcsetattr ( STDIN_FILENO, TCSANOW, &oldt );
  
  return ch;
}

Any help on this would be of great help...

This exact code works for me perfectly

[ahamed101]

Hi,
Please find the code snippet...

#include <stdio.h>
#include <termios.h>
#include <unistd.h>

int mygetch ( void )
{
  int ch;
  struct termios oldt, newt;

  tcgetattr ( STDIN_FILENO, &oldt );
  newt = oldt;
  newt.c_lflag &= ~( ICANON | ECHO );
  tcsetattr ( STDIN_FILENO, TCSANOW, &newt );
  ch = getchar();
  tcsetattr ( STDIN_FILENO, TCSANOW, &oldt );

  return ch;
}

int main()
{
	char ch;

	ch = mygetch();

	printf("\n Entered Character : %c",ch);

	return EXIT_SUCCESS;
}

I have to press enter twice only then the character gets printed.
One more instance...

#include <stdio.h>
#include <termios.h>
#include <unistd.h>

int mygetch ( void )
{
  int ch;
  struct termios oldt, newt;

  tcgetattr ( STDIN_FILENO, &oldt );
  newt = oldt;
  newt.c_lflag &= ~( ICANON | ECHO );
  tcsetattr ( STDIN_FILENO, TCSANOW, &newt );
  ch = getchar();
  tcsetattr ( STDIN_FILENO, TCSANOW, &oldt );

  return ch;
}

int main()
{
	char ch;

	printf("\n Hello World");
	printf("\n Press any key to continue...");
	mygetch();

	return EXIT_SUCCESS;
}

Here also I need to press enter twice only then the second message gets displayed "Press any key to continue..."

Platform : HP-UX

Any suggestions would be of great help...

Thank You

[Aia]

if the function returns an int what do you think the variable that stores that value should be in main?
Either terminate the literal string in printf with a \n or make a call to fflush(stdout) after.
Otherwise there's not guarantee that it will display when you want.
A call to exit() requires the inclusion of the standard header file stdlib.h

[ahamed101]

I tried flushing the outpur stream... but no luck... I still need to press enter thrice... i did a gdb and found out that at this line ch = getchar() the program waits for extra two more enter to be pressed...

Is there something to do with the terminal settings?... I tried this in FreeBSD, its working fine... but in HP-UX, AIX its not and it is there where I want to use...

[ahamed101]

Guys, any suggestions?

[Salem]

Without access to your platform, I've got nothing.

Apart from reading the manuals very carefully.
Focus on tcsetattr, tcgetattr and termios.

There may be some other thing you have to call, possibly right at the start of the program before you do any I/O (including printf).

Finding a forum specific to your platform may also help, if there is such a thing.

[ahamed101]

Hi Salem,
I am using HP-UX machine...
Yes I am searching other forums also, nothing helps... Hope to get around this somehow...

[ahamed101]

Hi All,

newt.c_cc[VMIN] = 1;
newt.c_cc[VTIME] = 0;

need to set this... it worked and thanks a lot to frk who helped me in this...